This project involves the longitudinal study of a group of 14-year- old rhesus monkeys and two generations of their progeny, all of whom live year-round in a 5-acre enclosure on the grounds of the NIHAC. The 14-year-old adults were all laboratory born, hand- reared in a nursery, and subsequently put together as a mixed-sex peer group. Despite the fact that none of these now middle-aged monkeys (nor any of their progeny) have had any physical exposure to any other monkeys, since they were first moved outdoors as juveniles they have consistently exhibited the full compliment of species-normative social behavior and group organization reported to date for rhesus monkeys born and living in feral environments. During document the species-normative patterns of social- emotional development, overall group organization, and seasonally-based patterns of behavioral and hormonal change that to date have characterized this laboratory-born group. Data from a second study of captive-born monkeys revealed a plausible proximate basis for maintenance of within-matriline cohesion, so characteristic of wild rhesus monkey troops, through changes in the preferred partners of offspring associated with the birth of an infant into the matriline. A third study initiated during the past year has focused on the phenomenon of pubertal male emigration as it occurs within wild-born rhesus monkey troops. Data from this semi-field study will include periodic measures of physical and hormonal maturation and hypothalamicpituitary-adrenal and psychophysiological response to dominance encounters, in addition to the behavioral measures typically obtained in field studies.